Bet Me by Jennifer Crusie

Minerva Dobbs knows that happily-ever-after is a fairy tale, especially with a man who asked her to dinner to win a bet. Even if he is gorgeous and successful Calvin Morrisey. Cal knows commitment is impossible, especially with a woman as cranky as Min Dobbs. Even if she does wear great shoes and keeps him on his toes. When they say good-bye at the end of their evening, they cut their losses and agree never to see each other again.

But Fate has other plans, and it's not long before Min and Cal meet again. Soon, they're dealing with a jealous ex-boyfriend, Krispy Kreme donuts, a determined psychologist, chaos theory, a freakishly intelligent cat, Chicken Marsala, and more risky propositions than either of them ever dreamed of. Including the biggest gamble of all—true love.